On the 29th November 1979, an Air New Zealand sightseeing flight over Antarctica crashed into Mount Erebus, killing all 237 passengers and 20 crew and leaving the wreckage and their bodies stranded in the polar ice. It was then the fourth worst accident in aviation history, and still remains New Zealand’s deadliest disaster in peacetime. But unlike Frank Marshall’s Alive or Robert Zemeckis’ Flight, Charlotte Purdy’s documentary Erebus: Into The Unknown focuses not on the crash itself and the victims’ last moments, but rather on the clean-up operation conducted by ordinary New Zealand street cops to recover the bodies and bring them back to their loved ones for burial. Part talking-heads and part reconstruction, it’s an affecting look at the little people caught up in a tragic event and a big corporation cover-up.

Interviewing police sergeants Stuart Leighton and Greg Gilpin (among others), Erebus: Into The Unknown retraces the steps of Operation Overdue, as they are sent out on a recovery mission to the Antarctic. Arriving at an American base with a few hastily grabbed jumpers, they’re given a crash course in polar survival, only to soon find themselves jumping out of a helicopter into the white, bottomless void of whirling snow. Unprepared and untrained for the devastation that confronts them, the men spend two weeks recovering personal effects and bodies (and protecting them from rapacious birds) to the point of physical and mental collapse. It’s a recovery mission only, not an investigation, but when they discover the Captain’s log book – a vital piece of evidence which is later tampered with – focus shifts onto Air New Zealand’s internal investigation, aiming to frame the pilot for navigational error amidst a frenzy of document shredding.

A producer on New Zealand TV, Charlotte Purdy makes her directorial debut with Erebus: Into The Unknown and it’s a well-crafted documentary, drawing on the testimonies of the traumatised policemen to give voice to the largely dialogue-free reconstructions. The dramatic episodes are competent enough, creating a very Seventies atmosphere through production design and costume, and lending the interviewees’ eye-witness accounts an unspoken fear, strength and dignity. And yet, perhaps due to the significance of the event in New Zealand’s history, the story becomes muddled, as it swerves from the human encounter with death on a catastrophic scale to conspiracy, cover-up and recrimination. The recovery mission lacks the dramatic urgency of survival documentaries such as Kevin Macdonald’s Touching The Void which it at times recalls, and yet neither does it quite muster the journalistic wherewithal to bring new evidence to light and expose Air New Zealand’s cowardly cover-up.

There’s no doubt it’s great to see the policemen finally recognised for their superhuman achievement, and while the wider context surrounding the air disaster is fascinating, Erebus: Into The Unknown doesn’t know which story to tell, unable to restrict itself either to the incredible task of ordinary heroes sent into the frozen desert to bring back bodies or to lift the lid on corporate conspiracy. But as either a tribute to those policemen who braved Antarctica or as a polemic on the airline’s corporate dishonesty, Erebus Into The Unknown nevertheless brings New Zealand’s worst disaster into the bright white light.

EREBUS: INTO THE UNKNOWN is released in cinemas on 9th January and on DVD/On Demand on 12th January